Our long-term goal is to understand behavior and social interactions as processes of adaptation to the problems that individuals face in their natural environment. The research is carried out on free- ranging primates, primarily the baboon population of the Amboseli Reserve, Kenya, which is the subject of a series of ongoing studies by P. I. and his colleagues. The research proposed for the next five years would approach the sociobiology of primates in four ways: through research on group ecology (Projects 1-4), on social interactions (Projects 5-8), on the spatial deployment of individuals within groups (Projects 9-11), and through the development of formal social theory and methods for quantitative analysis of social behavior and group structure (Projects 12-17). The projects are as follows: (1) Demography and group dynamics under changing ecological conditions; (2) Effects of tree mortality on group behavior; (3) Foraging strategies and selective feeding as ways of meeting nutritional requirements; (4) Effects of predation and of communicable diseases on differential mortality, fecundity, and group demography; (5) Effects of dominance status stability on differential reproduction; (6) Kin selection and the allocation of altruistic behavior; (7) Infant development and the social milieu; (8) Social networks and spatial deployment; (9) Causes and effects of peripheralization; (10) Kinship and group geometry; (11) Composition and dynamics of subgroups; (12) Estimating relative frequency of behavior and duration-in-state from time-in-state; (13) Dyadic comparisons and other relations; (14) Classification of languages; (15) Best estimates of rates of behavior and social interaction; (16) The model of sender-receiver independence; and (17) Handling the "clearing- house" case.